Can somebody please help me?

Hi there! First of all, let me say that I think it's great that you're trying to apply what you've learned thus far! Kudos!

But, make no mistake, this is not a small project. I think flexbox could be good here, but you might also consider a Bootstrap grid. But before you venture out on this quest (that I suspect is a little larger than you think it is), I'd like to point you in the direction of Trello. Essentially, it's a cloud-based to do list app, but I use it to help me organize my projects. You can make a "board" and then add lists with to-do lists to track progression and due dates etc. It is both simple and brilliant.

Start breaking this down. I challenge you to just get the landing page done and responsive. And even that will take some work. And break down the landing page. Make small attainable goals and make them as small as possible. Make a list like "add navigation bar", "add logo", "add picture 1". And as you start checking these off, I think you'll be surprised at how quickly it actually begins to look and feel like what you have in your mind.

The bonus to breaking down a project like this, is that you become adept at doing so. So when you move onto the contact page etc, you already have a good idea of what needs to be done and about how long it will take. You will also likely have had to fix a few problems on the first page that you're less likely to repeat on the one you're working on.

The more you practice at doing a project in this way, the more time-efficient you will become. So I'd concentrate on getting it done, and less on efficiency for the time being.

Hope this helps!